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Old December 20, 2009, 11:17 PM   #1
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Different Max Powder loads

New to relaoding and beginning to work up my first series of .308 loads with IMR 4064 and 165 gr SGK (SBT).

Can someone help me upderstand why the Sierra manual lists the max 4064 load at 43.5 gr and the Speer manual lists 45.0 for a 165 gr SBT?

The minimum loads are also different at 41.0 gr for Speer and 37.6 gr for Sierra.

I just trying to get and idea of the range I should be working in to optimize the load for my rifle.

Thanks in advance.
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Old December 21, 2009, 02:20 AM   #2
Crusty Deary Ol'Coot
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Even'in Gardien,

Yep, the answer is simple, and boils down to the fact that the different companies are using different test rifles/barrels, more then likely different lots or powder, primers, cases as well as the different bullets.

Personally I look, if possible, at a number of books when begining to develop loads and then start toward the bottom of the listing for my first tests.

Normally I will progress with one grain increases - example 40 grains to 41 grains - until I am approaching the upper listed loads at which time I begin to go in 1/2grain increases.

If the books said something like a starting load of 35gr. and a max of 41, my load series might look something like this -- 3 rounds 35gr., 3 at 36, 3 at 37, 3 at 38, 3 at 38.5, 3 at 39, 3 at 39.5, 3 at 40, 3 at 40.5 and 3 at 41grains.

How low I begin, somewhat depends on how much experience I have with that rifle in other tests.

If you begin to experience any of the signs of high pressure - read lots and heed the warnings!! - it is time to stop, go home and pull the bullets on the hot loads.

I like to run my tests over the cronograph at the same time I am shooting groups, as watching the velocities as well as pressures and group sizes at the same time can provide a lot of information.

Back awhile, I used to always shoot 5 shot groups, but shooting 3 shot groups is much cheaper when using bullets such as the Nosler partitions, and it provides a good working idea of what the potential of the load is.

A few years back, I worked up loads for a 300win mag, and then needed to buy more powder, which of course was then of a different lot #.

Just the change in powder lots, decreased my velocities by about 50fps.

Be very aware that using cases, even of the same brand, can create high pressures providing they are not of the same manufacturing lot #s.

Because of past experience, I try to avoid using odd lot cases for anything other then "banger" or lower pressure practice ammo.

Buy your brass as many of one lot as you can afford, and once you have found a good powder for your needs, buy a number of pounds of that powder making sure it is all of the same lot #.

But, beaware that for example if the "book" says the max load is 45grains and you find your rifle's sweet spot at 43 grains, when you change lots of powder you may need to adjust up or even down to again find what your rifle likes.

It is fantastic that we have such great products, but everything is made within tolerences, a fact we must take into consideration during load development.

Read, be safe and enjoy!

Keep em coming!

Crusty Deary Ol Coot
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Old December 21, 2009, 07:04 AM   #3
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+1, The biggest differences are using different brand bullets with the same weight. The shape, and therefore the bearing surface (the amount of the bullet that actually touches the barrel) is one of the biggest causes of the differences in max charges.

I usually use three load manuals and take an average of the max charges as mine.

I wrote an article on how I do load development on my website, it might help you out.
Owner of & Chief Instructor for The Southern Marksman, LLC
NRA Life Member, NRA CRSO, Multi-Discipline NRA Certified Instructor
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Old December 21, 2009, 09:32 AM   #4
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Try 42.5 grains IMR 4064 with your 165 grain bullet.
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Old December 21, 2009, 09:43 AM   #5
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Outstanding responses, Gentlemen. I very much appreciate the education.

Crusty, your process of 1 grain increments then to half is exactly what I was planning to do.

Will start today and see what happens.

Merry Christmas!
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Old December 21, 2009, 03:31 PM   #6
Crusty Deary Ol'Coot
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Go for it!

I have reloaded for a goodly number of years, starting back when, with Herters equipment.

Now that was a learning experience! Had a set of their 243 dies that looked like they had been reamed with a pipe tap.

But then, maybe that wasn't so bad back then, as I had a browning A-bolt of much more recent production and it had a barrel rifled with a threading tap!

It would shoot anything for beans!!!!!!!!!! Would begin to hold a candle to the RUGER Hawkeye that replaced it!

Anyway, be safe and enjoy!!!!!!!!!!!!!!

AND, remember the reason for the season, the Christ of CHRISTmas!

Keep em coming!

Crusty Deary Ol Coot
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